Earlier this summer, as I perused my race schedule, it occurred to me that I didn’t have anything on the calendar that would, by its very nature, challenge me to my core.

Sure, there are always PRs to seek and sprints to gut out. But those are optional challenges, not goals that promise to pull your guts out and show you what you’re made of.

Until Saturday, that is.

The Betsy Owens Memorial Swim in Lake Placid is a two-mile cable course in beautiful, calm Mirror Lake. Nothing inherently difficult about it—just four laps around a cable. I traveled up to the race with the group I swim with at Lake Desolation, and I was excited for a chance to enjoy the fellowship of my swimmer-friends and go for a nice dip in a beautiful lake.

Excited, until I learned that the water temperature was 67 degrees.

I once got hypothermic during a 2.5-mile ocean swim in Florida, where the water temperature was at least 70 degrees. Ever since then, I’ve happily told anyone who asks that I don’t swim in water below 70 degrees without a wetsuit. So when word started rippling through the crowd that the water temperature was significantly below that, I started to panic a bit. I walked down to the shore to confirm the temperature with the lifeguard.

“Yep, 67,” she said. “It was even colder a couple years ago. People were getting out after the first lap.”

“I might get out after the first lap today,” I said, laughing.

The thought lodged in my head immediately: I might get out after the first lap. If I need to, I can get out after the first lap. If I want to, I can get out after the first lap.

The water: Chilly, but so beautiful!

The thought stayed with me as my friends went to warm up (certainly an oxymoron, when warming up involves jumping in a cold lake). When they returned to the beach, shivering, they insisted the water wasn’t as bad as it sounded. I raised my eyebrows.

“OK, it’s bad,” said one friend. “It takes your breath away. You just have to tell yourself: ‘I’m fine. I just need to take deep breaths and stretch out my strokes.'”

How seriously did I take my swim? As seriously as a Wonder Woman bathing suit.

I nodded. And before I knew it, I was lined up at the shoreline in my Wonder Woman bathing suit, feeling about as far away from a comic-book superheroine as I could get.

Here’s the really cruel part of this story: The start involved the dozen waves of swimmers to wade out to a buoy about 10 yards from shore, then tread water by the buoy for up to two minutes while waiting for the fastest waves to go.

My first step into the water was fine—just a little bit chilly. But lowering my torso into the water literally took my breath away. I thought about how the race director swam the English Channel last year, surviving 64-degree temperatures for 10 hours. And I thought one last time about how I could get out after one lap if I wanted. I dolphin-dived into the silver-gray water, whimpering to myself as I submerged.

Something funny: The next two minutes were among the most fun I’ve ever had swimming. There’s a special kind of camaraderie that forms between those doing the same absurd thing at the same time. I can’t even tell you what me and my other 10 wave-mates yammered about as we waited for our turn to start; I just know that if I saw those swimmers on the street, I’d hug them, and thank them for helping me to not feel so alone.

The first wave was a cold, gray blur. I tried to follow my swimmer-friend’s advice: You’re fine. Breathe. Fine. Breathe. By the time I finished the first lap, I was swimming alone, without knowing whether I’d passed my wave-mates or whether they passed me. I stayed that way for the rest of the race, seeing other swimmers only when they passed me on the opposite side of the cable course.

I kept it smooth and relaxed for the second and third laps. As I rounded the buoy to start the fourth and final lap, I got ready to sprint.

That’s when the cold really hit. My limbs felt numb and clumsy. My arms slapped the water; my kick felt out of rhythm. I actually wondered whether I was moving forward, or just splashing around in place. It felt like I was swimming for hours before I spotted the finish buoy.

As I ran onto shore, my feet felt like ice blocks. Someone grabbed me and wrapped me in a space blanket. It was done.

I finished in 56 minutes and change—a little slower than I’d hoped, but a victory nonetheless. As I sat under a blanket with my swim-buddies, my favorite Eleanor Roosevelt quote popped into my head: You must do the thing you think you cannot do. It doesn’t matter how long the swim took me, or that I doubted myself before I started. When faced with the thing I thought I could not do, I said: “I’ll try.”